Fuel injection systems for internal combustion engines

ABSTRACT

A device for generating a voltage pulse for use with a fuel injection system of an internal combustion engine utilizing infra-red radiation source and detector for obtaining a voltage pulse to operate the solenoids of the appropriate fuel injectors in cyclic order, which voltage pulse is timed from shutter means mechanically driven and interposed between the source and detector, transistorized circuitry including a plurality of transistors and a power transistor connected in cascade and inversely switched for fast switching the output from the detector in order to amplify it to operate the solenoid.

United States Patent [191 Ford [4 1 May 14,1974

1 1 FUEL INJECTION SYSTEMS FOR INTERNAL COMBUSTION ENGINES [75] Inventor: Eric Harold Ford, London, England [73] Assignee: Lumenition Limited, London,

England [22] Filed: Nov. 29, 1971 [21] Appl. No.: 202,979

Related U.S. Application Data [63] Continuation-impart of Ser. No. 874,470, Nov. 6,

[30] Foreign Application Priority Data Feb. 25, 1970 Great Britain ..'.....9049/70 ,1 PELL LJBZQ .NQEQ LB HQH 11 g--:---,:--4.!f1 7 [52] U.S.,Cl. 123/32 EA, 123/32 AB [51] Int. Cl. .Q F02b 3/00 [58] Field of Search 123/32 EA, 32 AB, 148 E; 317/141, 157; 250/8331, 217

[56] References Cited UNITED STATES PATENTS 3,605,712 9/1971 Ford 123/148 3,405,268 10/1968 Brunton 250/8331 3,473,067 10/1969 Rittmayer 250/217 SS 3,543,739 12/1970 Mennesson 123/119 3,390,668 7/1968 Hufton 123/148 3,646,926 3/1972 Plume 123/148 Primary ExaminerLaurence M. Goodridge Assistant ExaminerRonald B. Cox Attorney, Agent, or FirmLarson, Taylor & Hinds [57] ABSTRACT A device for generating a voltage pulse for use with a fuel injection system of an internal combustion engine utilizing infra-red radiation source and detector for obtaining a voltage pulse to operate the solenoids of the appropriate fuel injectors in cyclic order, which voltage pulse is timed from shutter means mechanically driven and interposed between the source and detector, transistorized circuitry including a plurality of transistors and a power transistor connected in cascade and inversely switched for fast switching the output from the detector in order to amplify it to operate the solenoid.

24 Claims) QPHEiiE s-L Q FUEL INJECTION SYSTEMS FOR INTERNAL COMBUSTION ENGINES CROSS REFERENCE This Application is a Continuation-in-Part application of my US. application Ser. No. 874,470 and relates in particular to certain improvements in the transistorized circuit which controls the operation of the solenoid of the fuel injection system disclosed therein.

FIELD OF INVENTION The present invention relates to improvements in fuel injection systems for internal combustion engines. Fuel injection systems offer many advantages over the conventional method of carburation and a number of different systems together with their associated electronics for operating the solenoids are well known.

DESCRIPTION OF THE PRIOR ART One such fuel injection system known as the Bosch EGGl-system employs electromagnetically actuated injection valves and solidstate circuitry for the metering of the injected fuel volume. The system is a pulsetimed manifold injection system, whereby the fuel is injected onto the heads of the intake valves by electromagnetically actuated nozzle valves. The quantity of fuel injected into each cylinder is a function of the prevailing operating conditions and is metered by the effective opening period of the nozzle valve. To reduce the number of components, especially in the electronic control unit, it has been found practical to common two injectors on four cylinder engines. The opening pulse for each group of injection valves is initiated by a trigger contact arrangement. One set of contacts generates a pulse for its group once every revolution of the camshaft. The trigger pulse upon closing of its contacts, both provides a current to open the respective group of injection valves and starts a time-delay circuit which in turn de-activates the injectors after a period which is determined by the fuel requirements as computed from the prevailing engine operating conditions.

The time-delay circuit is common for all injector groups and is switched from one group to the other by the trigger contacts in proper sequence. The electronic control unit receives its information from several sensing elements. The speed is obtained from the incoming triggering pulses. The load factor is measured by an in ductive pressure sensor. Full load operation is controlled by a vacuum operated switch, which switches the control unit over for an enriched mixture when the manifold vacuum has dropped below a predetermined level. On deceleration, moreover, the fuel is completely shut off to save fuel and to minimize the emission of unburnt fuel components.

The'electronic control unit contains one power amplifier for each group of injection valves and the time determining network. The power amplifiers are activated by the pulses received from the trigger contacts but only if the time determining circuitry is turned on too. A suitable logic warrants proper correlation between power amplifier and trigger contacts to exclude unwanted injections which could otherwise be trigstate by the triggering pulses. The on period of the multivibrator depends on the inductance of the manifold pressure sensor, but is modulated according to the non-linear requirements of the engine fuel characteristics by a corrective speed circuit.

-lhssls s some? qxiitssats 220 components including 25 transistors and 35 diodes. WM-Wm W The above described Bosch EGGI-system has the following disadvantages:

a. it relies on a contact breaker to generate the pulses for its operation. It is well known that mechanical contacts are liable to wear and unreliable in precision timing.

b. The electronic control unit is unduly complicated and contains a large number of electronic components. Therefore the overall failure rate due to component failure is too high.

c. The determination of the on state of the multivibrator which determines the quantity of fuel injected is achieved principally from the prevailing pressure in the manifold but is modified according to speed. The correct on period for the prevailing engine requirements is not easily achieved by the present system.

Another type of fuel injection system is disclosed in US. Pat. No. 3,543,739. In this system the fuel injector is operated by an electro-magnet which is energized from a photo-electric cell through an electronic relay and current limiter. The photo-electric cell receives its light from a lamp around which a screen having a triangular shaped window is rotated in synchronism with the engine. In addition to a main throttle there is an auxiliary throttle which regulates the injected fuel and which blocks either more or less of the air inlet conduit according to the flow, the movement of the auxiliary throttle being controlled by the difference in pressure between two chambers separated by a flexible diaphragm connected to the auxiliary throttle. The auxiliary throttle is also connected to the supports for the lamp and photo-electric cell so as to move these elements in relation to the window in the screen. Thus the greater the pressure difference in the inlet conduit across the auxiliary throttle, the greater the upward movement thereof, and the greater the time per revolution that the photo-electric cell is energized, thereby resulting in a greater amount of fuel being injected into the cylinder since the relay is energized for a longer period per revolution. Conversely, the opposite is true when the pressure starts to equalize across the auxiliary throttle. The electronic relay consists of two transistors arranged as a Darlington pair to form a pre-amplifier stage and a power transistor which forms a final amplification stage. The output from the power transistor is applied to the energizing winding of the electro-magnet via a diode.

It will be appreciated that at high engine revolutions absolute accuracy in the timing of the operation of the solenoid is essential otherwise misfiring will occur. Misfiring and bad timing will cause excessive black smoke in the exhaust fumes from the engine which is very undesirable in a society which is becoming more and more pollution conscious. The electronic relay disclosed in the above referred to patent is unable to cope with the high speed running conditions required by modern fuel injection systems, resulting in poor efficiency, high fuel consumption and excessive pollution to the atmosphere the human race has to breathe.

SUMMARY OF INVENTION It is therefore an object of the present invention to provide a fuel injection system which incorporates electronic switching and amplifying means which will cleanly energize and de-energize the solenoid to inject the correct amount of fuel at the correct instant in time into each cylinder in turn at all speeds from idling to maximum R.P.M.

It is further object of the invention to provide a fuel injection system for a road vehicle which will comply with the requirements of the Federal law due to come into operation in 1975, in that the timing is such that for all engine speeds, the fuel is fully burnt before being discharged into the atmosphere.

According to the present invention there is provided a device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a photo-transistor sensitive to infra-red radiation which will switch on or conduct when exposed to the radiation and switch off when the radiation is cut off; a gallium arsenide lamp emitting infra-red radiation; an element which is opaque to infra-red radiation positioned between the gallium arsenide lamp and the phototransistor, said opaque element having at least one aperture therein; means for moving the opaque element in timed relation to the engine revolutions; an amplifier having first and second transistors connected in cascade to the output of the photo-transistor and arranged to switch in inverse relation to one another so that at any one time a transistor is always fully saturated; and a power transistor connected to the output of the amplifier to be switched in inverse relation to the second transistor and connected in circuit relationship with the solenoid such that every time a beam of radiation falls onto and is cut off from the photo-transistor, said transistorized amplifier circuit and power transistor cause the fast switching of the solenoid .to inject the desired quantity of fuel into a cylinder of the internal combustion engine in accordance with the period during which the photo-transistor is exposed to infra-red radiation.

Means are preferably provided for controlling the air to fuel ratio in accordance with both the speed of rotation of the engine and also the load on the engine.

A fuel injector is preferably associated with a pair of cylinders, the cylinders being arranged in pairs so that the injectors can operate alternately. Each injector has a solenoid for its actuation, this solenoid being fed by the voltage pulses.

In a preferred embodiment, the gallium arsenide lamp and the photo-transistor are mounted on a stator member and the wall of a cup-shaped member having at least one slot therein rotates between the two infrared elements and constitutes the opaque element. Preferably, in the case of a four-cylinder engine, there is a pair of photo-transistors mounted I80 with respect to the rotating slot on the cup-shaped rotor member. The slot in the cup-shaped member may have a greater peripheral width at its closed end than at its open end, and the whole cup may be moved longitudinally with respect to the stator member according to engine speed. The stator member may be mechanically coupled to a diaphragm which is subjected to a difference in pressure between atmospheric and the pressure within the inlet manifold of the engine, so as to be longitudinally movable with respect to the rotor member according to the load on the engine.

The photo-transistor may have its base electrode left unconnected. The two transistors of the amplifier may be of like type, the emitter electrode of the phototransistor being connected to the base electrode of the first transistor, the collector electrode of the first transistor being connected to the base electrode of the second transistor, the collector electrode of the second transistor being connected to the base electrode of the power transistor, the emitter electrodes of the transistors being commoned and connected to one side of a battery, the collector electrodes being connected to the other side of the battery each through a resistor, and the base electrodes being connected to the commoned emitter electrodes each through further resistors.

Alternative arrangements include providing a pair of power transistors arranged as a darlington pair, and protecting these against positive going transients by a zener diode and resistor connected between the common collector electrodes and the base electrode of the first transistor. The photo-transistor which acts as an infra-red detector may be replaced by a photodarlington pair or triplet. Energy storage means in the form of an inductance may be connected between the collector electrode of the last stage of the amplifier and the base electrode of the power transistor.

BRIEF DESCRIPTION OF DRAWINGS The present invention will now be described in greater detail by way of example with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic block diagram of the fuel injection system for a six cylinder gasoline engine;

FIG. 2 is a diagrammatic view partly in section of a preferred form of device for generating a voltage pulse;

FIG. 3 is a circuit diagram showing the utilization of the voltage pulses to operate the fuel injection system shown in FIG. 1;

FIG. 4 is an elevation view of another type of device for fast switching the solenoid ofa fuel injection system of an internal combustion engine;

FIG. 5 shows the disc of the device shown in FIG. 4 having V-shaped slots;

FIG. 6 is a circuit diagram of an alternative form of the transistorized fuel injection system;

FIG. 7 is a circuit diagram showing a modified arrangement of the circuit shown in FIG. 6;

FIG. 8 is a circuit diagram of a third embodiment of the transistorized fuel injection system; and

FIG. 9 is a circuit diagram ofa fourth embodiment of the transistorized fuel injection system.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. I of the drawings the fuel injection system for a gasoline engine includes a pair of solenoid operated injectors 2 and 4 mounted in the air induction manifold 6. Each injector 2 or 4 supplies a group of three cylinders 8 or 10 respectively with a fuel-air mixture suitable for combustion through the appropriate inlet valves 12. The timing of the opening of each injector relative to the opening of the inlet valve is timed off the camshaft of the engine, the appropriate voltage pulse for the energization of the solenoid of the fuel injector being generated by the device shown in FIG. 2. The fuel injection system also includes a pump 14 which supplies fuel to the injectors from a fuel circuit including a fuel tank 16,-a filter l8 and a pressure regulator 20.

Referring now to FIG. 2, the device for generating the voltage pulses to energize the solenoids of the fuel injectors includes a cup-shaped rotor member 22 and a co-operating stator member 24, whose crosssectional shape as shown is in the form of a letter E, the cup-shaped member having an internal diameter which is greater than the diameter of the cylindrical centralsection of the stator member 24. Both members are displaceable independently relative to one another. The cup-shaped rotor member 22 is slideably mounted on a splined shaft 26 which is driven by the camshaft of the engine. The cup-shaped rotor member 22 has a slot 28 cut therein, said slot having one edge 29 which is parallel to the axis of the shaft 26 and a second edge 30 which is inclined at a slight angle to the edge 29 around the peripheral surface of the cylindrical cup so that the circumferential angle subtended by the slot is greater at its base 31 than at the open end. The state member 24 is connected to a shaft 32 the other end of which is secured to a diaphragm 34 housed within a chamber 36. The diaphragm 34 divides the chamber in half, one half of which is open to the atmosphere where the shaft 32 passes thereinto, whilst the other half is connected to the induction manifold 6 of the system so that the pressure on the diaphragm 34 is equal to the difference in pressure between the partial vacuum within the manifold and the atmospheric pressure. A compression spring 38 is positioned in an extension 40 to the chamber 36 the ends of which respectively engages the end of the extension 40 and one face of the diaphragm 34. The spring 38 restores the diaphragm 34 to its normal position when there is no difference in pressure thereacross.

The stator member 24 comprises a cylindrical central part 42 which is free to move within the cup-shaped rotor member 22 and an annular wall 44 which concentrically surrounds the cylindrical central part 42. The central cylindrical part 42 houses a pair of gallium arsenide lamps 46 and 46 arranged in opposition to one another around the periphery of the central part 42. Instead of using gallium arsenide lamps any other forms of lamp emitting infra-red radiation such as a BETA lamp may be used. The annular wall 44 houses a pair of silicon planar photo-transistors 48 and 48' arranged in opposition to one another around the inner periphery of the annular wall 44, the components of each pair facing one another across the gap between the central part 42 and the annular wall 44.

In one preferred embodiment the photo-transistors 48 and 48 are photo darlington amplifiers.

The cup-shaped rotor member 22 which is driven from the camshaft of the engine is mounted on the splined shaft 26 and is mechanically connected to governor means (not shown) so as to be longitudinally displaceable on the shaft 26 according to the speed of the engine. As shown in FIG. 2, the cup-shaped rotor member 22 moves to the left with increasing speed and to the right with decreasing speed. Thus with increasing speed the photo-transistors 48 and 48 are exposed to the radiation of the respective gallium arsenide lamps for a greater percentage of the camshaft revolution. The state member 24 is also longitudinally displaceable with respect to the rotor member 22, by means of the diaphragm 34 which is subject to the difference in pressure between atmosphere and the pressure prevailing within the inlet manifold. Thus with high manifold vac uum the diaphragm 34 is sucked in towards the inlet manifold against the action of the restoring spring 38 which causes the stator member to move to the left as shown in FIG. 3. This has the effect of decreasing the injection duration. Conversely, under low manifold vacuum conditions the stator member moves to the right thus increasing the arc during which the phototransistors remain illuminated by the gallium arsenide lamps and thus increasing the injection duration.

The electronic part of the system is shown in FIG. 3, and includes the gallium arsenide lamps 46 and 46', the photo-transistors 48 and 48 and solenoids 50 and 50' of respective fuel injectors 2 and 4. The electronic system for each injector is entirely separate except that they are both energized by the 12 volt battery supply, the components in each part being identical. Resistors 52 and 52 are connected in series with the respective gallium arsenide lamps 46 and 46' across the 12 volt supply, and the voltage across the lamps is stabilized by means of zener diodes 54 and 54'. Resistors 56, 56', 58 and 58' are in the emitter-collector paths of the respective photo-transistors 48 and 48 also across the 12 volt battery supply. As stated above the photo-transistors 48 and 48' are energized from the gallium arsenide lamps 46 and 46 when infra-red radiation passes through the slot 28 in the cup-shaped rotor member 22. Capacitors 60 and 60' are connected between the collector electrode of the respective photo-transistors 48 v and 48' and ground so as to stabilize the voltage and prevent oscillations occurring thereacross.

The circuit further includes pairs of transistor amplifiers 62, 64 and 62', 64 and high voltage power transistors 66 and 66. The pairs of transistors 62, 64 and 66 are of like type, e.g., NPN silicon transistors. Resistors 68, 68 and 70, 70' are in collector paths of the respective transistors 62, 62, 64 and 64. Resistors 72, 72, 74 and 74 are connected between the base electrodes of the respective transistors 64, 64, 66 and 66' and the 12 volt supply. Capacitors 76 and 76 are connected between the emitter electrode of the respective phototransistors 48 and and the base electrode of the respective power transistors 66 and 66' to provide some positive feed-back to assist switching under all conditions. The output from the photo-transistors 48 and 48' is applied to the base electrode of the transistors 62 and 62' whose output in turn is applied to the base electrodes of the transistors 64 and 64'. The transistors 62 and 62' will switch in inverse relation to the transistors 64 and 64, that is when the transistors 62 and 62 are on, transistors 64 and 64 are off and vice versa. The output from these latter transistors is applied to the power transistors 66 and 66, whose output passes through the respective solenoid windings 50 and 50'. The power transistors 66 and 66 also switch in inverse relation to the transistors 64 and 64'. Hence with the photo-transistors 48 and 48on and consequentl with transistors 62 and 62' on, transistors 64 and 64' will be off and power transistors 66 and 66' will be on. Resistors 80 and 80 reduce the induced voltage applied to the power transistor on switching.

The solenoid 50 of the injector 2 is controlled by means of the photo-transistor 48 and likewise the solenoid of the injector 4 is controlled by means of the photo-transistor 48. The injectors 2 and 4 are each associated with a group of three cylinders in the engine. Since the photo-transistors 48 and 48' are energized alternately on rotation of the rotor 22 the injectors 2 and 4 operate alternately. The normal sequence of firing in a six cylinder internal combustion engine is I-V- III-VI-II-IV and in order that the injectors can operate alternately, the first injector 2 is associated with cylinders Nos. I, II and III and the second injector 4 is associated with cylinder Nos. IV, V and VI as indicated diagrammatically in FIG. 1.

The operation of the above described fuel injection system for a six cylinder gasoline engine is as follows. On rotation of the camshaft the photo-transistors 48 and 48' are alternately illuminated by infra-red radiation as the edge 29 of the slot 28 uncovers their respective gallium arsenide lamps 46 and 46. Conduction of the respective photo-transistors 48 and 48' is amplified by means of the associated inverse switching transistors 62, 64 and 64, 64' to open the respective power transistors 66 and 66. Conduction of these power transistors energizes the respective solenoids in alternate sequence to operate the respective injectors 2 and 4. When the edge 30 of the slot 28 alternately recovers the infra-red radiation sources, the photo-transistors 48 and 48' cease to conduct immediately and the respective power transistors 66 and 66 are switched off, through the inverse switching of the transistors 62, 64 and 64, 64, to de-energize the solenoids 50 and 50' of the injectors 2 and 4. The amount of fuel injected into each cylinder depends on the arc of the circle during which the associated photo-transistor is exposed to infra-red radiation, or in other words the peripheral width ofthe slot 28 at the point which intersects the radiation path between the infra-red source and the photo-transistor. The air to fuel ratio is made richer whenever the peripheral width of the radiation window is increased and it is made leaner whenever the width of the radiation window is decreased. As explained above, this may be caused by the longitudinal movement of the rotor 22 with respect to the stator 24, or the longitudinal movement of the stator 24 with respect to the rotor 22, or a combined movement of both members.

Whilst the embodiment described above applies to a six cylinder gasoline engine, it is equally applicable to any other type of engine such as a four, eitht or twelve cylinder engine. The cylinders may be paired or otherwise grouped so as to reduce the number of injectors and electronic systems required. For example in the case of a four cylinder engine, the cylinders may be paired in accordance with the Bosch EGGI-system previously referred to.

Referring next to FIGS. 4 and which show a modified form of device for generating the voltage pulses to energize the solenoids, the device includes a cupshaped housing 82, an opaque disc 84 mounted on a shaft 86 which is driven by the camshaft of the engine. The shaft 86 is supported within the housing 82 by means of a bearing 87. The disc 84 is provided with a single V-shaped slot 88 which is cut therein into the circumference of the disc. It should be noted that the sides of the V-shaped slot are not radial with respect to the centre of the disc but slightly inclined thereto so that the base of the V-shaped slot which is slightly curved terminate well before the centre of the disc. Mounted for rotation within the cup-shaped housing 82 is a disc 89. Two solid state infra-red radiation sources 46 and 46' such as a gallium arsenide lamps and two radiation sensitive semiconductor devices 48 and 48 such as a photo-transistor are located on opposite ends of a square C-shaped members and 85' which are keyed into and radially slidable on the disc 89. These two members 85 and 85 are arranged diametrically opposite one another.

As the disc 84 is rotated by the camshaft of the engine the radiation sensitive elements 48 and 48 are exposed to infra-red radiation from the respective solid state sources 46 and 46 every time they are uncovered by the V-shaped slot 88. When the infra-red radiation falls onto the radiation sensitive element 48 or 48' it is energized to initiate operation of the respective transistorized fuel injection circuit described more fully in FIG. 6. As will be explained more fully hereinafter it is at the actual moment that the infra-red radiation is cut off that the solenoid is enegized to inject the fuel into the cylinder in question. The slotted disc 8 is analogous to the cup-shaped rotor member shown in FIG. 2, and is therefore applicable to engines having four, six or more cylinders.

In order to achieve an advance or retard of the fuel injection to allow for different engine speeds and/or loads, the square C-shaped members 85 and 85 can be moved either radially with respect to the disc 89, i.e., within a keyed slot referred to above, or they can be moved circumferentially by rotating the disc 89 relative to the housing 82. In the former case the apparent positions of the infra-red sources 46 and 46' and radiation sensitive elements 48 and 48' are displaced along the lines Y-Y relative to the disc 84. In view of the fact that the sides of the slot 88 are not radial the time during which the solenoid is energized per cycle is reduced as the line of sight is moved radially inwards. In the latter case the apparent positions of the infra-red sources 46 and 46 and radiation sensitive elements 48 and 48' are displaced along the lines ZZ relative to the disc 84, to provide an actual retard or advance of the timmg.

Referring to FIG. 6, in which the circuit applicable to only one of the sources 46, 46 and radiation sensitive elements 48, 48 is shown, the circuit includes as in the previously described embodiment, the gallium arsenide lamp 46, the photo-transistor 48, the power transistor 66 and the solenoid 50. The photo-transistor 48 is intermittently energized by infrared radiation from the gallium arsenide lamp 46 when the radiation is permitted to pass through the V-shaped slot 88 in the disc 84. A zener diode Z is connected across the lamp 46 for the purpose of stabilizing the voltage thereacross. The circuit also includes transistors 61, 62 and 64 and resistors Rl to R6. The emitter electrodes of the phototransistor 48, the power transistor 66 and the three transistors 61, 62 and 64 are all directly connected to ground. The collector electrode of the photo-transistor 48 is connected to the base electrode of the transistor 61 and to the positive terminal of the battery (+12 volts) through the resistor R4. The collector electrode of the transistor 61 is connected to the base electrode of the transistor 62 and to the positive terminal of the battery through the resistor R3. Next, the collector electrode of the transistor 62 is connected to the base electrode of the transistor 64 and to +12 volts through the resistor R2. Similarly, the collector electrode of the transistor 64 is connected 'to the base electrode of the power transistor 66 and to +12 volts through the resistor RI. The base electrode of the power transistor 66 is connected to ground via a 33 ohm resistor R6. The

collector electrode of the power transistor 66 is connected to one end of the solenoid 50 and also to ground through the resistor R5, the other side of the solenoid being connected to the positive terminal of the battery.

As in the previous embodiment the circuit is duplicated for the fuel injector associated with the other group of cylinders.

The resistance values of the resistors R1 to R4 is pref erably arranged such that:

where n is an integer preferably between and inclusive. The actual resistance of R1 is preferably equal to 22 ohms. This arrangement assists the fast switching and ensures that the transistor go from a fully saturated condition to a fully non-conductive condition and vice versa.

The operation of the above described circuit is as follows. As soon as the photo-transistor 48 is energized with infra-red radiation from the lamp 46, it conducts. This causes the base electrode of the transistor 61 to bottom thus switching it off. The transistor 62 is switched hard on, i.e., to the fully saturated condition and causes the transistor 64 to be switched hard off by reason of its base electrode becoming bottomed. The power transistor 66 is switched on, and the solenoid 50 is energized. At the instant the infra-red radiation is cut off, the photo-transistor 48 switches off, the transistor 61 switches on, the transistor 62 switches off, the transistor 64 switches on and the power transistor 66 switches off causing the solenoid to become deenergized. It will be appreciated that the transistors will switch in inverse relation to one another and that every on transistor is fully saturated and every off transistor completely non-conducting.

Referring now to the modification shown in FIG. 7, it will be seen that the photo-transistor 48 has been re placed by a darlington pair consisting of a phototransistor 48 and a transistor 49, the collector electrodes being connected in common to the +12 volt supply through the resistor R4, and to the base electrode of the transistor 61 through a pair of series diodes 54 and 5 5. These diodes are provided to raise the voltage across the darlington pair 48-49. The emitter electrode of the photo-transistor transistor 48 is connected to the base electrode of the transistor 49 as is conventional with a darlington pair. The operation of this circuit is otherwise identical with that described in FIG. 6.

The advantage of the circuit shown in FIG. 7 is that the darlington pair 48-49 provides pre-amplification of the output from the detector before it is applied to the fast switching trigger proper. Normally, the output from a photo-transistor is only a few microamps so that in order to achieve the necessary current to operate the solenoid a large current amplification must be effected by each stage of the trigger. By using a photodarlington pair the amplification per stage can be cut down to 5 with the circuit of FIG. 6 as modified by FIG. 7.

The magnitude of the currents flowing through the resistors Rl to R4 is:

R4 l6mA R3 80mA Rl 2.0A

which means that a current of 10 amps is available for the solenoid.

A third modified transistorized circuit is shown in FIG. 8, and includes the gallium arsenide lamps 46 and 46' the photo-transistors 48 and 48' and the solenoids 5t) and 50 of the respective fuel injectors. The electronic system for each injector is again entirely separate except that they are both energized by the 12 volt battery supply, the components in each part being idenv tical. The voltage supply to the gallium arsenide lamps 46 and 46 is obtained through respective resistors 52 and 52 and stabilized by means of zener diodes Z and Z. Resistors 51 and 51' are in series with respective lamps 46 and 46 connected across the zener diodes Z and Z. The photo-transistors 48 and 48 each form the first part of a photo-darlington pair, the second part being a respective one of transistors 49 and 49. The emitter-collector path of each photo-darlington pair is in series with a respective one of resistors 53 and 53 across the zener diodes Z and Z.

The inverse switching amplifier part of the system includes three cascaded transistors 61, 62 and 64 for thefirst half of the circuit and transistors 61, 62' and 64' for the second half of the circuit. The input to the base electrode of the first transistor 61 or 61 is obtained through a pair of diodes 54 and 55 or 54 and 55' across respective resistors 58 and 58. This part of the circuit also includes resistors 67, 68, and 72 or 67, 68, 70 and 72 together with respective diodes 76 and 76 interposed between the second and third stages of this inverse switching current amplifier.

The output from each of the respective third stage transistors 64 and 64 is applied to the base electrode of a respective one of power transistors 66 and 66 through an inductance L or L. Respective resistors 74, 74', 80 and 80' connect the base and collector electrodes respectively of the power transistors to ground.

The purpose of the inductance L or L is to store energy in the form of a magnetic field when the transistor 64 or 64' is off and the base of the power transistor 66 or 66' is being supplied with current through the inductance L or L. When the radiation is cut off from the darlington pair 4849 or 4849 the pair switches off, transistor 61 or 61 switches on, transistor 62 or 62' switches off, the transistor 64 or 64 switches on and the power transistor 66 or 66 switches off to effect the magnetic collapse of the field in the respective solenoid 50 or 50. The voltage across the inductance L or L' is reduced to zero instantaneously. However as is well known, by Lenzs law, the .current through the inductance L or L cannot be reduced to zero instantaneously due to collapse of the magnetic field associated with the inductance. The energy stored in this field is dissipated as current supply to the base of transistor 66 or 66 so slowing down the switch-off of the power transistor. Thus any solenoid voltage spike is prevented.

The inductance L or L is preferably iron coredand each has the additional advantage that if the operating voltage is abnormally high the inductance slows the switch-off of the respective power transistor 66 or 66 even more than for normal operating voltage. Thus a more stable energizing voltage is generated in the respective solenoid winding 50 or 50'. The inductance reduces the effect of variation in the supply, therefore, as well as eliminating any voltage spike.

Clearly the respective diodes 54, 55 and 54', 55' could be replaced by a single diode provided that this raises the voltage across the darlington pair to a sufficient value to permit satisfactory operation of the circuit. Also the photo-darlington pair could be replaced by a photo-darlington triplet to obtain even higher amplification prior to the fast inverse switching trigger proper.

The above described circuit has the following additional advantages over that described in the previously described embodiments.

a. there are no condensers used in the circuit resulting in minimum oscillation in the solenoid winding.

b. Due to the presence of the inductances lower voltage power transistors can be used.

Referring now to FIG. 9, the circuit is yet a further improvement of the trigger. For the sake of clarity, only one such transistorized circuit has been shown, but it will be appreciated that two or more identical circuits can be provided for operating two or more fuel injector solenoids. The circuit differs from that shown in FlG. 8 in so far as there is no photo-darlington pair 48-49 and no series diodes 54 and 55. Like reference numerals refer to like components in the previous figures and will not be further referred to, except where it is necessary to understand the modifications to the circuit.

The modified circuit includes diodes 100, 102, 103 and 109; resistors 101, 105 and 108; a zener diode 104; and power transistors 106 and 107 arranged as a darlington pair.

The diode 100 and resistor 101 are provided for the purpose of clean switching and stabilization of the trigger. The diode 100 is connected across the phototransistor 48. It has the effect of reducing the interelectrode capacitance between these two electrodes and thus enables the photo-transistor to switch cleanly when it receives the infra-red radiation from the gallium arsenide lamp 46. The diode 100 thus permits the use of a high gain photo-transistor without multiple switching or oscillation. The resistor 101 provides negative feed-back from the collector electrode of the transistor 62 to the base electrode of the transistor 61.

The diode 102 which is in series with the inductance L between the collector electrode of the transistor 64 and the base electrode of the first transistor 106 of the darlington pair power stage, prevents voltage surges induced in the inductance L, when the power transistors 106 and 107 switch on, from breaking down the transistor 64 which has just switched off.

The zener diode 104 and resistor 105 are provided in order to protect the power transistors 106 and 107 against positive going transients induced in the solenoid on switching. It will be appreciated that due to the fast switching of the solenoid brought about by the trigger, even though the inductance L will limit any sudden collapse of the magnetic field in the solenoid, nevertheless the power transistors under these conditions are vulnerable to be broken down by positive going transients. Thus, if there are any positive going transients whilst the two power transistors are non-conductive, the zener diode 104 will conduct above a certain voltage level to raise the base voltage of the power transistor 106 sufficiently to turn the power transistors on before the voltage exceeds a value at which the transistor will break down. The resistor 105 limits the ultimate current which will flow in the base circuit of the transistor 106 once the zener diode 104 conducts.

The diodes 103 and 109 protect the power transistors 106 and 107 from breaking down due to negative going transients.

1n the embodiments of FIGS. 8 and 9, the opaque element Q may be either the cup-shaped rotor member 22 and co-operating stator member 24 as shown in FIG. 2 or the slotted disc shaped member 84 shown in FIG. 5.

In all the circuits previously described, the inverse switching trigger is arranged such that there is always one transistor in the fully saturated condition whilst the transistors immediately adjacent thereto are completely non-conducting. The fully saturated transistor or transistors acts as a short-circuit path to any transients which may be induced in the circuit during operation. This short-circuit path provided by the fully saturated transistors ensures that the off transistor or transistors cannot be broken down by these transients.

The additional protective devices shown in the circuit of FIG. 9 such as the zener diode 104 and the diodes 103 and 109 provide additional protection for the power transistors 106 and 107 against positive and negative going transients respectively.

What 1 claim and desire by Letters Patent is:

1. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a photo-transistor which will conduct when exposed to radiation and cease to conduct when the radiation is cut off;

a solid state infra-red radiation source; a disc having at least one V-shaped slot cut therein, said disc being positioned between the radiation source and the photo-transistor;

means for rotating the disc in timed relation to the engine;

means for moving the line of sight between the radiation source and the photo-transistor relative to the disc so as to achieve an advance or retard of the timing of the fuel injection;

an amplifier having three transistor stages arranged in cascade with their emitter electrodes all directly grounded to switch in inverse relation to one another such that there is always one transistor fully saturated at any one time;

three collector resistors connecting the collector electrodes of the three resistors to a positive sup- P y;

a power transistor connected to the output of the last stage of the amplifier to be switched in inverse relation to said last transistor stage, the power transistor being connected in circuit with the solenoid so that every time a slot permits the infra-red radiation to fall onto and be cut off from the phototransistor, the amplifier and power transistor cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the photo-transistor is exposed to infrared radiation;

and energy storage means connected between the output of the last transistor of the amplifier and the base electrode of the power transistor, said device further comprising a diode connected across the base-emitter electrodes of the first transistor and a resistor which interconnects the collector electrode of the second transistor with the base electrode of the first transistor.

2. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion engine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off;

a pair of gallium arsenide lamps;

an element which is opaque to infra-red radiation positioned between the elements of each pair of lamps and photo-transistors, the elements of each pair being at 180 from one another with respect to the opaque element, said opaque element having a single slot cut therein;

means for rotating the opaque element in timed relation to the engine;

means for moving the line of sight between the gallium arsenide lamps and respective phototransistors relative to the opaque element so as to achieve an advance or retard of the timing of the fuel injection;

a pair of amplifiers each having an odd numbered plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at any one time;

a pair of power transistors connected to the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel into associated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to radiation, each said amplifier having first, second and third transistors, the emitter electrodes of which are coupled directly to ground and the collector electrodes of which are each connected to a positive supply voltage through respective first, second and third collector resistors, the values of resistance of which are such that the resistance of the second resistor is n times the value of the third resistor and the resistance of i the first resistor is n squared times the value of the third resistor,-n being any positive integer between 15 and inclusive; v 3. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion engine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off;

a pair of gallium arsenide lamps; an element which is opaque to infra-red radiation po- 6 sitioned between the elements of each pair of lamps and photo-transistors, the elements of each pair being at from one another with respect to the opaque element, said opaque element having a single slot cut therein;

means for rotating the opaque element in timed relation to the engine;

means for moving the line of sight between the gallium arsenide lamps and respective phototransistors relative to the opaque element so as to achieve an advance or retard of the timing of the fuel injection; a pair of amplifiers each having an odd numbered plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at any one time;

a pair of power transistors connected to the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel intoassociated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to readiation, each said amplifier having three transistors and an iron cored inductance being connected between the base electrode of the power transistor and the collector electrode of the third transistor in each amplifier and a diode being connected between the collector electrode of the second transistor and the base electrode of the third transistor in each amplifier.

4. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion en'- gine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off;

a pair of gallium arsenide lamps;

an element which is opaque to infra-red radiation positioned between the elements of each pair of lamps and photo-transistors, the elements of each pair being at 180 from one another with respect to the opaque element, said opaque element having a single slot cut therein;

means for rotating the opaque element in timed relation to the engine;

means for moving the line of sight between the gallium arsenide lamps and respective phototransistors relative to the opaque element so as to achieve an advance or retard of the timing of the fuel injection;

a pair of amplifiers each having an odd numbered plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at any one time;

a pair of power transistors connected to the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel into associated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to radiation, each said amplifier having three transistors, an an inductance and diode being connected in series between the base electrode of the power transistor and the collector electrode of the third transistor in each amplifier. 5. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion engine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off;

a pair of gallium arsenide lamps; an element which is opaque to infra-red radiation positioned between the elements of each pair of lamps and photo-transistors, the elements of each pair being at l80 from one another with respect to the opaque element, said opaque element having a single slot cut therein; means for rotating the opaque element in timed relation to the engine; means for moving the line of sight between the gallium arsenide lamps and respective phototransistors relative to the opaque element so as to achieve an advance or retard of the timing of the fuel injection;

a pair of amplifiers each having an odd number plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at one time;

a pair of power transistors connectedto the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel into associated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to radiation, an additional transistor being arranged with each phototransistor to form a darlington pair, and a pair of series connected diodes being provided to connect the output from the photo-darlington pair to the first transistor of each amplifier.

6. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a radiation sensitive element which will switch on when exposed to radiation and switch off when the radiation is cut off;

a solid state infra-red radiation source;

an element opaque to infra-red radiation positioned between the radiation source and the radiation sensitive element and having at least one slot therein;

means for rotating the opaque element in timed relation to the engine revolutions;

meansfor moving the line of sight between the radiation source and the radiation sensitive element in relation to the opaque element so as to achieve an advance or retard of the timing of the fuel injection;

a transistorized circuit including an amplifier having a plurality of transistors arranged in cascade and fed from the output of the radiation sensitive element and arranged to fast switch in inverse relation to one another so that at any one time a transistor is always fully saturated;

a pair of power transistors formed as a darlington pair and connected to the output of the amplifier means to be switched in inverse relation to the last transistor of the amplifier means and connected in cir cuit with the solenoid so that every time the slot permits a beam of infra-red radiation to fall onto and be cut off from the radiation sensitive element, the transistorized amplifier means and darlington pair power transistors cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the radiation sensitive element is exposed to infra-red radiation;

energy storage means connected to the base electrode of the first transistor of the darlington pair; and means for protecting the power stage against induced positive and negative going transients at the instant of switch off.

7. A device according to claim 6, wherein the means for protecting the darlington pair power transistors against. induced positive going transients comprises a zener diode and a resistor connected in series between the commoned collector electrodes and base electrode of the first transistor of the darlington pair.

8. A device according to claim 6, wherein the means for protecting the darlington pair power transistors against induced negative going transients comprises a diode connected across the commoned collector electrodes and the emitter electrode of the second transistor of the darlington pair.

9. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a photo-transistor sensitive to infra-red radiation which will conduct when exposed to infra-red radiation and switch off when the radiation is cut off;

a gallium arsenide lamp emitting infra-red radiation;

an element opaque to infra-red radiation positioned between the photo-transistor and the gallium arsenide lamp, said opaque element having at least one slot therein;

means for rotating the opaque element in timed relation to the engine revolutions;

an amplifier having first, second and third transistors connected in cascade to the output of the phototransistor and arranged to switch in inverse relation to one another so that at any one time a transistor is always fully saturated;

a pair of power transistors arranged as a darlington pair and connected to the output of the third transistor of the amplifier to be switched in inverse relation to the third transistor of the amplifier and connected in circuit relationship with the solenoid;

and an inductance connected between the output of the third transistor of the amplifier and the power transistors, whereby everytime the slots permits a beam of infra-red radiation to fall onto and be cut off from the photo-transistor, the amplifier and power transistors in association with the inductance cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the photo-transistor is exposed to infra-red radiation.

10. A device according to claim 9, wherein a zener diode and resistor are connected in series between the commoned collector electrodes of the two power transistors and the base electrode of the first transistor, so as to turn on the power transistors in the event of a positive going transient occurring when these transistors are non-conducting.

ll. A device according to claim 9, wherein a first diode is connected between ground and the base electrode of the first power transistor and a second diode is connected between ground and the commoned collector electrodes in order to prevent negative going transients from breaking down the power transistors when they are non-conducting.

12. A device according to claim 9 wherein a diode is connected in series with the inductance.

13. A device according to claim 9, wherein a diode is connected across the photo-transistor to enable clean switching to take place.

14. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, comprising a radiation sensitive element which will switch on when exposed to radiation and switch off when the radiation is cut off;

a solid state infra-red radiation source; 7

an element opaque to infra-red radiation positioned between the radiation source and the radiation sensitive element and having at least one slot therein;

means for rotating the opaque element in timed relation to the engine revolutions;

means for moving the line of sight between the radiation source and the radiation sensitive element in relation to the opaque element so as to advance or retard the timing of the fuel injection;

a transistorized circuit including an amplifier having a plurality of transistors arranged in cascade and fed from the output of the radiation sensitive element and arranged to fast switch in inverse relation to one another so that at any one time a transistor is always fully saturated;

a power transistor connected to the output of the am plifier means to be switched in inverse relation to the last transistor of the amplifier means and connected in circuit with the solenoid so that every time the slot permits a beam of infra-red radiation to fall onto and be cut off from the radiation sensitive element, the transistorized amplifier means and power transistor cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the radiation sensitive element is exposed to infra-red radiation; and an inductance connected between the output of the last transistor of the amplifier and the base electrode of the power transistor.

15. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a photo-transistor sensitive to infra-red radiation which will switch on or conduct when exposed to the radiation and switch off when the radiation is cut off;

a gallium arsenide lamp emitting infra-red radiation;

a zener diode connected in parallel with the gallium arsenide lamp;

a resistor connected in series with the parallel combination of zener diode and gallium arsenide lamp across a battery;

an element which is opaque to infra-red radiation positioned between the gallium arsenide lamp and the photo-transistor, said opaque element having at least one aperture therein;

means for moving the opaque element in timed relation to the engine revolutions;

an amplifier having first and second transistors of like type connected in cascade to the output of the photo-transistor and arranged to switch in inverse relation to one another so that at any one time a transistor is always fully saturated; and a power transistor connected to the output of the amplifier to be switched in inverse relation to the second transistor and connected in circuit relationship with the solenoid, said photo-transistor having its base electrode left unconnected and its emitter electrode connected to the base electrode of the first transistor, said first-transistor having its collector electrode connected to the base electrode of the second transistor, said second transistor having its collector electrode connected to the base electrode of the power transistor, the emitter electrodes of the transistors being commoned and connected to one side of the battery, the collector electrodes being connected to the other side of the battery each through a resistor, and the base electrodes being connected to the commoned emitter electrodes each through further resistors, said transistorized amplifier circuit and power transistor causing the fastswitching of the solenoid to inject the desired quantity of fuel into a cylinder of the internal combustion engine in accordance with the period during which the photo-transistor is exposed to infra-red radiation.

16. A device according to claim 11, wherein the photo-transistor has a resistor in its collector circuit whose value of resistance is R4 where R4 n Rl, where n is an integer between 15 and 20 inclusive.

17. A device according to claim 11, wherein the photo-transistor is arranged as a darlington pair with an additional transistor, the commoned collector electrodes being in circuit with a resistor whose value of resistance if R4 where R4 n Rl where n is an integer between 15 and 20 inclusive.

18. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a radiation sensitive element which will conduct when exposed to radiation and cease to conduct when the radiation is cut off;

a solid state infra-red radiation source; a disc having at least one V-shaped slot therein, said disc being positioned between the radiation source and the radiation sensitive element;

means for rotating the disc in timed relation to the engine;

means for moving the line of sight between the radiation source and the radiation sensitive element relative to the disc so as to achieve an advance or retard of the timing of the fuel injection;

'an amplifier having an odd numbered plurality of transistor stages arranged in cascade with their emitter electrodes all directly grounded to switch in inverse relation to one another such that there is always one transistor fully saturated at any one time;

three collector resistors connecting the collector electrodes of the three resistors to a positive supply, the values of the resistance of the resistors being such that:

R2 nRl and R3 n Rl R l R2 and R3 representing the resistances of the third, second and first collector resistors and n being a positive integer between and inclusive;

a power transistor connected to the output of the last stage of the amplifier to be switched in inverse relation to said last transistor stage, the power transistor being connected in circuit with the solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from the radiation sensitive element, the amplifier and power transistorcause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the radiation sensitive element is exposed to the infra-red radiation.

19. A device according to claim 5, wherein each gallium arsenide lamp is connected in series with a first resistor and each photo-darlington pair is connected in series with a second resistor, and wherein a zener diode is connected across each lamp/photo-darlington pair so as to form a parallel circuit therewith.

20. A device according to claim 14, wherein the solid state infra-red radiation source comprises a gallium arsenide lamp and the radiation sensitive element comprises a darlington pair comprised of a photo-transistor and a transistor.

21. A device according to claim 14, wherein the solid state infra-red radiation source, the radiation sensitive element and a zener diode are connected in parallel to provide a substantially constant current throughthese elements irrespective of the battery voltage.

22. A device according to claim 1, wherein if R1, R2 and R3 are the resistance values of the resistors connected in the collector circuit of the third, second and first transistors of the cascaded amplifier, then R2 nRl and R3 n Rl where n is an integer between l5 and 20 inclusive.

23. A device according to claim 18, wherein the radiation sensitive element comprises a photo-transistor, said photo-transistor having a resistor in its collector circuit whose value of resistance is R4 where R4 n Rl, where n is an integer between l5 and 20 inclusive.

24. A device according to claim 18, wherein the radiation sensitive element comprises a photo-transistor and is arranged as a darlington pair with an additional transistor, the commoned collector electrodes being in circuit with a resistor whose value of resistance is R4 where R4 n Rl where n is an integer between 15 and 20 inclusive. 

1. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a phototransistor which will conduct when exposed to radiation and cease to conduct when the radiation is cut off; a solid state infra-red radiation source; a disc having at least one V-shaped slot cut therein, said disc being positioned between the radiation source and the photo-transistor; means for rotating the disc in timed relation to the engine; means for moving the line of sight between the radiation source and the photo-transistor relative to the disc so as to achieve an advance or retard of the timing of the fuel injection; an amplifier having three transistor stages arranged in cascade with their emitter electrodes all directly grounded to switch in inverse relation to one another such that there is always one transistor fully saturated at any one time; three collector resistors connecting the collector electrodes of the three resistors to a positive supply; a power transistor connected to the output of the last stage of the amplifier to be switched in inverse relation to said last transistor stage, the power transistor being connected in circuit with the solenoid so that every time a slot permits the infra-red radiation to fall onto and be cut off from the phototransistor, the amplifier and power transistor cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the photo-transistor is exposed to infra-red radiation; and energy storage means connected between the output of the last transistor of the amplifier and the base electrode of the power transistor, said device further comprising a diode connected across the base-emitter electrodes of the first transistor and a resistor which interconnects the collector electrode of the second transistor with the base electrode of the first transistor.
 2. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion engine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off; a pair of gallium arsenide lamps; an element which is opaque to infra-red radiation positioned between the elements of each pair of lamps and photo-transistors, the elements of each pair being at 180* from one another with respect to the opaque element, said opaque element having a single slot cut therein; means for rotating the opaque element in timed relation to the engine; means for moving the line of sight between the gallium arsenide lamps and respective photo-transistors relative to the opaque element so as to achieve an advance or retaRd of the timing of the fuel injection; a pair of amplifiers each having an odd numbered plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at any one time; a pair of power transistors connected to the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel into associated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to radiation, each said amplifier having first, second and third transistors, the emitter electrodes of which are coupled directly to ground and the collector electrodes of which are each connected to a positive supply voltage through respective first, second and third collector resistors, the values of resistance of which are such that the resistance of the second resistor is n times the value of the third resistor and the resistance of the first resistor is n squared times the value of the third resistor, n being any positive integer between 15 and 20 inclusive.
 3. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion engine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off; a pair of gallium arsenide lamps; an element which is opaque to infra-red radiation positioned between the elements of each pair of lamps and photo-transistors, the elements of each pair being at 180* from one another with respect to the opaque element, said opaque element having a single slot cut therein; means for rotating the opaque element in timed relation to the engine; means for moving the line of sight between the gallium arsenide lamps and respective photo-transistors relative to the opaque element so as to achieve an advance or retard of the timing of the fuel injection; a pair of amplifiers each having an odd numbered plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at any one time; a pair of power transistors connected to the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel into associated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to readiation, each said amplifier having three transistors and an iron cored inductance being connected between the base electrode of the power transistor and the collector electrode of the third transistor in each amplifier and a diode being connected between the collector electrode of the second transistor and the base electrode of the third transistor in each amplifier.
 4. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion engine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off; a pair of gallium arsenide lamps; an element which is opaque to infra-red radiation positioned between the elements of each pair of lamps aNd photo-transistors, the elements of each pair being at 180* from one another with respect to the opaque element, said opaque element having a single slot cut therein; means for rotating the opaque element in timed relation to the engine; means for moving the line of sight between the gallium arsenide lamps and respective photo-transistors relative to the opaque element so as to achieve an advance or retard of the timing of the fuel injection; a pair of amplifiers each having an odd numbered plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at any one time; a pair of power transistors connected to the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel into associated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to radiation, each said amplifier having three transistors, an an inductance and diode being connected in series between the base electrode of the power transistor and the collector electrode of the third transistor in each amplifier.
 5. A device for fast switching a pair of solenoids of a fuel injection system of an internal combustion engine, including a pair of photo-transistors which will conduct when exposed to radiation and cease to conduct when the radiation is cut off; a pair of gallium arsenide lamps; an element which is opaque to infra-red radiation positioned between the elements of each pair of lamps and photo-transistors, the elements of each pair being at 180* from one another with respect to the opaque element, said opaque element having a single slot cut therein; means for rotating the opaque element in timed relation to the engine; means for moving the line of sight between the gallium arsenide lamps and respective photo-transistors relative to the opaque element so as to achieve an advance or retard of the timing of the fuel injection; a pair of amplifiers each having an odd number plurality of transistor stages arranged in cascade to switch in inverse relation to one another such that there is always one transistor in each amplifier fully saturated at one time; a pair of power transistors connected to the output of the last stage of respective amplifiers to be switched in inverse relation to said last transistor stage, each power transistor being connected in circuit with a respective solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from each photo-transistor in turn, the amplifiers and respective power transistors in turn cause the fast switching of respective solenoids to inject the desired quantity of fuel into associated cylinders of the internal combustion engine in accordance with the period in which the gallium arsenide lamps are exposed to radiation, an additional transistor being arranged with each photo-transistor to form a darlington pair, and a pair of series connected diodes being provided to connect the output from the photo-darlington pair to the first transistor of each amplifier.
 6. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a radiation sensitive element which will switch on when exposed to radiation and switch off when the radiation is cut off; a solid state infra-red radiation source; an element opaque to infra-red radiation positioned between the radiation source and the radiation sensitive element and having at least one slot therein; meaNs for rotating the opaque element in timed relation to the engine revolutions; means for moving the line of sight between the radiation source and the radiation sensitive element in relation to the opaque element so as to achieve an advance or retard of the timing of the fuel injection; a transistorized circuit including an amplifier having a plurality of transistors arranged in cascade and fed from the output of the radiation sensitive element and arranged to fast switch in inverse relation to one another so that at any one time a transistor is always fully saturated; a pair of power transistors formed as a darlington pair and connected to the output of the amplifier means to be switched in inverse relation to the last transistor of the amplifier means and connected in circuit with the solenoid so that every time the slot permits a beam of infra-red radiation to fall onto and be cut off from the radiation sensitive element, the transistorized amplifier means and darlington pair power transistors cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the radiation sensitive element is exposed to infra-red radiation; energy storage means connected to the base electrode of the first transistor of the darlington pair; and means for protecting the power stage against induced positive and negative going transients at the instant of switch off.
 7. A device according to claim 6, wherein the means for protecting the darlington pair power transistors against induced positive going transients comprises a zener diode and a resistor connected in series between the commoned collector electrodes and base electrode of the first transistor of the darlington pair.
 8. A device according to claim 6, wherein the means for protecting the darlington pair power transistors against induced negative going transients comprises a diode connected across the commoned collector electrodes and the emitter electrode of the second transistor of the darlington pair.
 9. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a photo-transistor sensitive to infra-red radiation which will conduct when exposed to infra-red radiation and switch off when the radiation is cut off; a gallium arsenide lamp emitting infra-red radiation; an element opaque to infra-red radiation positioned between the photo-transistor and the gallium arsenide lamp, said opaque element having at least one slot therein; means for rotating the opaque element in timed relation to the engine revolutions; an amplifier having first, second and third transistors connected in cascade to the output of the photo-transistor and arranged to switch in inverse relation to one another so that at any one time a transistor is always fully saturated; a pair of power transistors arranged as a darlington pair and connected to the output of the third transistor of the amplifier to be switched in inverse relation to the third transistor of the amplifier and connected in circuit relationship with the solenoid; and an inductance connected between the output of the third transistor of the amplifier and the power transistors, whereby everytime the slots permits a beam of infra-red radiation to fall onto and be cut off from the photo-transistor, the amplifier and power transistors in association with the inductance cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the photo-transistor is exposed to infra-red radiation.
 10. A device according to claim 9, wherein a zener diode and resistor are connected in series between the commoned collector electrodes of the two power transistors and the base electrode of the first transistor, so as to turn on the power transistors in the event of a positive going transient occurring when these transistors are non-conducting.
 11. A device according to claim 9, wherein a first diode is connected between ground and the base electrode of the first power transistor and a second diode is connected between ground and the commoned collector electrodes in order to prevent negative going transients from breaking down the power transistors when they are non-conducting.
 12. A device according to claim 9, wherein a diode is connected in series with the inductance.
 13. A device according to claim 9, wherein a diode is connected across the photo-transistor to enable clean switching to take place.
 14. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, comprising a radiation sensitive element which will switch on when exposed to radiation and switch off when the radiation is cut off; a solid state infra-red radiation source; an element opaque to infra-red radiation positioned between the radiation source and the radiation sensitive element and having at least one slot therein; means for rotating the opaque element in timed relation to the engine revolutions; means for moving the line of sight between the radiation source and the radiation sensitive element in relation to the opaque element so as to advance or retard the timing of the fuel injection; a transistorized circuit including an amplifier having a plurality of transistors arranged in cascade and fed from the output of the radiation sensitive element and arranged to fast switch in inverse relation to one another so that at any one time a transistor is always fully saturated; a power transistor connected to the output of the amplifier means to be switched in inverse relation to the last transistor of the amplifier means and connected in circuit with the solenoid so that every time the slot permits a beam of infra-red radiation to fall onto and be cut off from the radiation sensitive element, the transistorized amplifier means and power transistor cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the radiation sensitive element is exposed to infra-red radiation; and an inductance connected between the output of the last transistor of the amplifier and the base electrode of the power transistor.
 15. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a photo-transistor sensitive to infra-red radiation which will switch on or conduct when exposed to the radiation and switch off when the radiation is cut off; a gallium arsenide lamp emitting infra-red radiation; a zener diode connected in parallel with the gallium arsenide lamp; a resistor connected in series with the parallel combination of zener diode and gallium arsenide lamp across a battery; an element which is opaque to infra-red radiation positioned between the gallium arsenide lamp and the photo-transistor, said opaque element having at least one aperture therein; means for moving the opaque element in timed relation to the engine revolutions; an amplifier having first and second transistors of like type connected in cascade to the output of the photo-transistor and arranged to switch in inverse relation to one another so that at any one time a transistor is always fully saturated; and a power transistor connected to the output of the amplifier to be switched in inverse relation to the second transistor and connected in circuit relationship with the solenoid, said photo-transistor having its base electrode left unconnected and its emitter electrode connected to the base electrode of the first transistor, said first transistor having its collector electrode connected to the base electrode of the second transistor, said second transistor having its collector electrode connected to the base electrode of the power transistor, the emitter electrodes of the transistors beiNg commoned and connected to one side of the battery, the collector electrodes being connected to the other side of the battery each through a resistor, and the base electrodes being connected to the commoned emitter electrodes each through further resistors, said transistorized amplifier circuit and power transistor causing the fast switching of the solenoid to inject the desired quantity of fuel into a cylinder of the internal combustion engine in accordance with the period during which the photo-transistor is exposed to infra-red radiation.
 16. A device according to claim 11, wherein the photo-transistor has a resistor in its collector circuit whose value of resistance is R4 where R4 n3R1, where n is an integer between 15 and 20 inclusive.
 17. A device according to claim 11, wherein the photo-transistor is arranged as a darlington pair with an additional transistor, the commoned collector electrodes being in circuit with a resistor whose value of resistance if R4 where R4 n3R1, where n is an integer between 15 and 20 inclusive.
 18. A device for fast switching the solenoid of a fuel injection system of an internal combustion engine, including a radiation sensitive element which will conduct when exposed to radiation and cease to conduct when the radiation is cut off; a solid state infra-red radiation source; a disc having at least one V-shaped slot therein, said disc being positioned between the radiation source and the radiation sensitive element; means for rotating the disc in timed relation to the engine; means for moving the line of sight between the radiation source and the radiation sensitive element relative to the disc so as to achieve an advance or retard of the timing of the fuel injection; an amplifier having an odd numbered plurality of transistor stages arranged in cascade with their emitter electrodes all directly grounded to switch in inverse relation to one another such that there is always one transistor fully saturated at any one time; three collector resistors connecting the collector electrodes of the three resistors to a positive supply, the values of the resistance of the resistors being such that: R2 nR1 and R3 n2R1 R1, R2 and R3 representing the resistances of the third, second and first collector resistors and n being a positive integer between 15 and 20 inclusive; a power transistor connected to the output of the last stage of the amplifier to be switched in inverse relation to said last transistor stage, the power transistor being connected in circuit with the solenoid so that every time a slot permits infra-red radiation to fall onto and be cut off from the radiation sensitive element, the amplifier and power transistor cause the fast switching of the solenoid to inject the desired quantity of fuel in a cylinder of the internal combustion engine in accordance with the period in which the radiation sensitive element is exposed to the infra-red radiation.
 19. A device according to claim 5, wherein each gallium arsenide lamp is connected in series with a first resistor and each photo-darlington pair is connected in series with a second resistor, and wherein a zener diode is connected across each lamp/photo-darlington pair so as to form a parallel circuit therewith.
 20. A device according to claim 14, wherein the solid state infra-red radiation source comprises a gallium arsenide lamp and the radiation sensitive element comprises a darlington pair comprised of a photo-transistor and a transistor.
 21. A device according to claim 14, wherein the solid state infra-red radiation source, the radiation sensitive element and a zener diode are connected in parallel to provide a substantially constant current through these elements irrespective of the battery voltage.
 22. A device according to claim 1, wherein if R1, R2 and R3 are the resistance values of the resistors connected in the collector circuit of the third, second and first transistors of the cascaded amplifier, then R2 nR1 and R3 n2R1 where n is an integer between 15 and 20 inclusive.
 23. A device according to claim 18, wherein the radiation sensitive element comprises a photo-transistor, said photo-transistor having a resistor in its collector circuit whose value of resistance is R4 where R4 n3R1, where n is an integer between 15 and 20 inclusive.
 24. A device according to claim 18, wherein the radiation sensitive element comprises a photo-transistor and is arranged as a darlington pair with an additional transistor, the commoned collector electrodes being in circuit with a resistor whose value of resistance is R4 where R4 n3R1, where n is an integer between 15 and 20 inclusive. 